When a vehicle's weight goes beyond a threshold of about 20 metric tons it is frequently more cost effective to use a vehicle power train that incorporates a large internal combustion engine such as a diesel engine connected to a generator. Through appropriate control systems, the generator powers electric motors for final drives in individual axles. This type of power train enables a great deal of flexibility in the application of torque, speed, and/or braking to individual wheels for the vehicle. Such a feature is particularly advantageous for off-road vehicles that have to negotiate difficult and un-even terrain.
Such vehicles have service brake assemblies adjacent the wheel powered by the final drive. In addition, such vehicles require park brakes to hold the vehicle stationary when it is not in an operational mode. Typically, park brakes have been incorporated somewhere on the electric motor shaft that is connected to the wheel hub through a speed reduction transmission. These park brake assemblies have the disadvantage of crowding the overall installed envelope for the electric motors and making it difficult to direct high current cables from the motor to a central current supply and control system for the vehicle.
In addition, it becomes difficult to service such park brakes because it usually is necessary to remove the wheel assembly and then remove the motor to gain access to the park brake. Braking systems have a finite service life so that periodic maintenance and replacement is necessary over the vehicle life. By providing the park brake adjacent the motor, servicing costs and complexity are greatly increased.
What is therefore needed in the art is a brake assembly avoiding the problems of the previous systems.